1. Field of the Invention
The present invention relates to a semiconductor device which is packaged for the mounting of a semiconductor component onto a circuit substrate, and to a method of manufacturing the same.
2. Description of the Related Art
There have been developed many types of packaging technologies including, as a typical one, quad flat pack (QFP). These packaging techniques are used to provide, at the time of mounting a semiconductor component onto a circuit substrate, facilitation of the protection and the mounting of semiconductor components. Because of the increase in connection terminal count in semiconductor components, the package size of semiconductor components is on the increase. Accordingly, it is becoming difficult for such conventional packaging technologies to deal effectively with demands for the reduction of mounting area.
With a view to meeting the demands, there has been devised a technique in which a bare semiconductor component is directly mounted onto a circuit substrate for the reduction and effective use of mounting area. For example, when a semiconductor component is connected to a circuit substrate, a layer of vapor-deposited adhesive metal or a layer of vapor-deposited diffusion protection metal is preformed on a terminal electrode of the semiconductor component and a projecting electrode of solder formed by plating is constructed overlying the layer. Subsequently, the semiconductor component is faced down and heated up to a high temperature. As a result of such application of heat, the solder is fused to a connection electrode of the circuit substrate. Such a mounting method is considered an effective technique because it can provide high post-connection mechanical strength and establish connection in a single process (xe2x80x9cIC MOUNTING TECHNOLOGYxe2x80x9d, edited by Japan Microelectronics Association, published on Jan. 15, 1980, Institute for Industrial Research).
In addition to the above-described method, there have been proposed other methods. For instance, U.S. Pat. No. 5,121,190 and Japanese Patent Application (unexamined) Pub. No. 6-61303 show mounting techniques and semiconductor devices in which a molding compound is used to secure the stability of solder joints. One such conventional semiconductor device will be described below by reference to FIGS. 7 and 8. FIG. 7 shows a layout of terminal electrodes of a commonly-used semiconductor component. FIG. 8 shows in cross section major parts of a conventional semiconductor device with a semiconductor component mounted face down.
In the terminal electrode layout of FIG. 7, terminal electrodes 16 are laid out around the periphery of a semiconductor component 15. In order to deal with an increase in the number of terminal electrodes 16, it is required to either reduce the gap between terminal electrodes 16 or increase the size of the semiconductor component 15 for coping with such an electrode number increase.
The semiconductor device of FIG. 8, in which the semiconductor component 15 is mounted face down, comprises, in addition to the semiconductor component 15, a terminal electrode 16 of the semiconductor component 15, a circuit substrate 17, a connection electrode 18 formed on a surface of the circuit substrate 17, a solder joint 19 which joints together the connection electrode 18 and the terminal electrode 16, a molding (sealing) resin 20 which seals the semiconductor component 15, and other structural elements.
A method of manufacturing a conventional semiconductor device having the above-described structure will be described below. In the first place, a projecting electrode of solder is preformed on the terminal electrode 16 of the semiconductor component 15. Thereafter, the semiconductor component 15 is mounted, in face down fashion, onto the circuit substrate 17. This is followed by alignment of the solder projecting electrode with a given position of the connection electrode 18. Next, the solder is melted by application of high-temperature heat (from 200 to 300 degrees centigrade), and the solder projecting electrode and the connection electrode 18 are joined together. In this way, the semiconductor component 15 is fixed to the circuit substrate 17 by the solder joint 19. Thereafter, a gap, created between the semiconductor component 15 and the circuit substrate 17, is filled with the molding resin 20 in the form of liquid. By heat hardening at about 120 degrees centigrade, the molding resin 20 is solidified. In this way, the mounting of the semiconductor component 15 onto the circuit substrate 17 is completed to provide a semiconductor device as shown in FIG. 8.
However, the above-described conventional semiconductor devices and associated manufacture methods have the following drawbacks.
Firstly, in order to protect the surface of the semiconductor component 15, it is required to fill a gap between the semiconductor component 15 and the circuit substrate 17 with the molding resin 20, and the mounting size increases accordingly. Therefore, when used as a packaged semiconductor device, its size becomes greater than that of the semiconductor component 15.
Secondly, if the number of terminal electrodes 16 of the semiconductor component 15 increases as the circuit scale increases, then the gap between adjacent terminal electrodes 16 is made narrower, resulting in reducing the size and the pitch of the solder joint 19 and consequently the reliability of the solder joint 19 between the semiconductor component 15 and the circuit substrate 17 will drop.
Thirdly, in order to facilitate the mounting of the terminal electrodes 16 laid out around the periphery of the semiconductor component 15 in face-down manner, it is required to use a multi-level wiring technique making use of a thin film technology for two-dimensionally placing the terminal electrodes 16 on the semiconductor component 15, to increase the size and the pitch of the terminal electrodes 16. However, such arrangement produces some problems, that is, semiconductor device yield is decreased and manufacturing costs are increased.
In view of the above, there is the limit of down-sizing semiconductor devices, improving their reliability to a further extent, and reducing their production costs and therefore the foregoing prior art techniques are not very practical. Particularly, in order to deal with the increase in the number of terminals in a semiconductor component, the above-described problems become increasingly serious.
The present invention was made with a view to providing solutions to the foregoing problems with the prior art techniques. Accordingly, an object of the present invention is to provide a down-sized, thinned, highly-reliable semiconductor device capable of dealing with higher terminal count, and a method of manufacturing the same.
One aspect of the present invention is a semiconductor device comprising:
(a) a semiconductor component;
(b) a circuit substrate;
(c) a base material which is placed between said semiconductor component and said circuit substrate; and
(d) a conductive paste, which is filled into a hole formed in said base material, for electrically connecting between a terminal electrode of said semiconductor component and an internal connection electrode of said circuit substrate.
Another aspect of the present invention is a semiconductor device comprising:
(a) a semiconductor component;
(b) a circuit substrate; and
(c) a conductive paste, which is filled into a hole formed in a surface of said circuit substrate at the side of said semiconductor component, for electrically connecting between a terminal electrode of said semiconductor component and an external connection electrode of said circuit substrate.
Still another aspect of the present invention is a method of manufacturing a semiconductor device in which a semiconductor component is mounted onto a circuit substrate, said semiconductor device manufacture method comprising:
(a) a hole forming step of forming a hole in a base material;
(b) a paste filling step of filling a conductive paste into said hole; and
(c) a connecting step of mechanically connecting said semiconductor component to said circuit substrate through said base material while at the same time electrically connecting between a terminal electrode of said semiconductor component and a connection electrode of said circuit substrate by said conductive paste.
Such arrangement eliminates the need for filling a gap between the semiconductor component and the circuit board (or the base material) with a molding resin, whereby the mounting size of semiconductor components can be reduced down to the size of semiconductor components.
Additionally, by the use of a multi-layered substrate for converting a layout of terminal electrodes placed around the periphery of a semiconductor component into a two-dimensional layout, it becomes possible to provide a semiconductor device capable of easily dealing with an increase in the number of terminal electrodes in a semiconductor component.